A classification scheme for earthworm populations (Lumbricidae) in cultivated agricultural soils in Brandenburg,Germany

Earthworm activity is observed at long‐term monitoring sites as an indicator of soil function to assess changes resulting from environmental and management conditions. In order to assess changes, characteristic values of earthworm populations under different site conditions have to be known. Therefore, a classification scheme for site‐specific earthworm populations was developed for soil in agricultural use, taking interactions between earthworm populations and soil properties into account. Characteristics of sites grouped by means of a cluster analysis after principal‐component analysis served as a basis for the derivation of the classification scheme. Soil variables found to characterize site differences with respect to earthworm populations were the texture of the topsoil, the texture of the subsoil, and the soil organic‐matter (SOM) content. The textural classes of the topsoil were divided into five groups comprising sandy soils (Ss), silty sand soils (Su), slightly loamy sand soils (Sl2), medium to strongly loamy sand soils (Sl3/Sl4), and loam and clay soils. Soil organic matter was divided into grades of equal size in a range from <1%, 1%–2% up to >6%. The variables “earthworm abundance” and “earthworm species” were selected to represent earthworm populations and were divided into six groups ranging from very low to extremely high. Defined groups of earthworm populations showed a clear structure in relation to soil textural groups and the content of SOM. From this distribution, a classification scheme was derived as basis for prognostic values of site‐specific earthworm populations, thus enabling the interpretation of changes over time. For some soil textural groups, selected variables appeared to enable the derivations of expected earthworm densities and species composition outside the range of the given database, but for some soil textural groups, broader databases will be needed to specify these derivations.     

冲积平原区土壤碳密度估算及其空间分布

冲积平原区通常具有复杂的剖面质地层次排列,为了准确估算冲积平原区土壤碳密度的空间分布特征,该文在华北冲积平原区的河北曲周县选取了121个土壤剖面,测定了各土层有机碳含量,构建了基于负指数函数的土壤有机碳垂向分布模型,结合地统计学方法绘制了该县土壤碳密度的空间分布图。结果表明,土壤有机碳含量随深度增加呈逐渐递减的趋势,各土层有机碳含量均属于中等变异程度。0~20和20~40 cm土壤有机碳空间连续性较好,它们的空间相关距离分别为14和3 km,而下层(40 cm)土壤有机碳均表现为纯块金效应结构。土壤有机碳垂向分布模型可以很好地描述剖面土壤有机碳含量的变化特征,且预测与实测的土壤有机碳含量的均方根误差仅为0.70 kg/m3,决定系数达到了0.95。曲周县土壤有机碳密度的空间分布总体表现为西北高东南低的趋势。其空间分布主要受土壤类型和质地的影响,其中潮土和盐化潮土的碳密度明显高于褐土化潮土,质地较细的土壤(轻壤、中壤和粘土)碳密度明显高于质地较粗的土壤(砂土和砂壤)。该研究为冲积平原区土壤碳密度的估算提供了一种新的方法。     

Spatial variability of bromide and atrazine transport parameters for a Udipsamment

Variability of soil properties can have major influence on the results of solute transport models when applied to field conducted experiments. The objective of this study was to determine spatial variability of transport and degradation parameters for a bromide tracer and atrazine herbicide in a 0.1 ha field of alluvial soils under no-till management. The soil investigated was a Sarpy (mixed, mesic Typic Udipsamment) with surface texture varying from sand to loam. The field was classified into three areas (Area I, sand; Area II, sandy loam; and Area III, loam) according to surface texture. Atrazine and bromide were applied at rates of 1.8 kg ha^− 1 and 115 kg ha^− 1, respectively. Soil cores were extracted at selected dates, segmented into 75 mm increments, and analyzed for each chemical separately. Soil physical and chemical properties were determined as a function of soil depth from additional soil cores removed when the transport study was completed. The value of the average pore water velocity, v, estimated using bromide concentrations was 6.0 mm day^− 1 which was about 29% lower than the value computed from meteorological information, 8.5 mm day^− 1. The average bromide dispersion coefficient (D), 508 mm² day^− 1, was 80 times higher than that for atrazine, 6.13 mm² day^− 1. The bromide v and D parameters were found to be spatially autocorrelated with ranges between 20 and 23 m and 12 and 24 m, respectively. Atrazine retardation and degradation parameters were found to have spatial structure for only one sampling date each with a range between 18 and 24 m. Soil textural parameters were found to have spatial structure for the first three depths (0–45 cm) of the five depths monitored (0–75 cm). This study found spatial autocorrelation within about 20 m for bromide transport parameters and a few atrazine transport parameters for an alluvial site.     

农田土壤质地空间分布的三维随机模拟及其不确定性评价

定量描述土体三维构型对于土地利用及农田水肥管理研究极其重要.本研究根据华北山前冲积平原区一块农田内的109个土壤剖面观测数据,运用马尔科夫地质统计学方法构建了土壤质地种类的三维空间分布模型,在100次随机模拟的基础上,分别得到了土壤质地种类的优化分布图及其概率分布图.结果表明,一维嵌入转移概率模型能很好地描述农田水平和垂直方向上各土壤质地种类的空间连续性及毗邻转移趋势.优化分布图虽能直观反映土壤质地种类的空间分布特征,但存在明显的平滑效应,不能刻画土壤质地种类空间分布的不确定性.而采用概率分布的方式来描述土壤质地种类空间分布的不确定性,能够有效地克服该缺点.     

Determination of Soil Type Boundaries using Electromagnetic Induction Scanning Techniques

Information on the spatial distribution of soil texture and soil water is vital in understanding crop yield variation. Such information allows improved management of all agricultural inputs. One of the limiting factors in the mapping of soil texture information, however, is cost.Confusion matrix analysis was used to determine whether bulk apparent electrical conductivity (ECa) data derived from electro-magnetic induction (EMI) scanning at field capacity, and clustered using a k-means algorithm, accurately delineates soil textural boundaries in a field containing clay loam and sandy loam soils.The ECa map was compared to two soil surveys, the first conducted at one sample per hectare and the second at four to eight samples per hectare. Using confusion matrix analysis a significantly stronger relationship was measured between the ECa map and soil units of the more intensive soil map, than with the lower sampling density soil survey. This relationship was between two classes of soil with a difference in clay content of 12% and two clusters with a difference in mean ECa of 16·9 mS m⁻¹.     

Proximal sensor-enhanced soil mapping in complex soil-landscape areas of Brazil

Portable X-ray fluorescence (pXRF) spectrometry and magnetic susceptibility (MS) via magnetometer have been increasingly used with terrain variables for digital soil mapping. However, this methodology is still emerging in many countries with tropical soils. The objective of this study was to use proximal soil sensor data associated with terrain variables at varying spatial resolutions to predict soil classes using the Random Forest (RF) algorithm. The study was conducted on a 316-ha area featuring highly variable soil classes and complex soil-landscape relationships in Minas Gerais State, Brazil. The overall accuracy and Kappa index were evaluated using soils that were classified at 118 sites, with 90 being used for modeling and 28 for validation. Digital elevation models (DEMs) were created at 5-, 10-, 20-, and 30-m resolutions using contour lines from two sources. The resulting DEMs were processed to generate 12 terrain variables. Total Fe, Ti, and SiO₂ contents were obtained using pXRF, with MS determined via a magnetometer. Soil class prediction was performed using the RF algorithm. The quality of the soil maps improved when using only the five most important covariates and combining proximal sensor data with terrain variables at different spatial resolutions. The finest spatial resolution did not always provide the most accurate maps. The high soil complexity in the area prevented highly accurate predictions. The most important variables influencing the soil mapping were MS, Fe, and Ti. Proximal sensor data associated with terrain information were successfully used to map Brazilian soils at variable spatial resolutions.     

Effect of Continuous Rice–Wheat Rotation on Soil Properties from Four Agro‐ecosystems of Indian Punjab

In Indian Punjab, rice–wheat is a dominant cropping system in four agro‐ecosystems, namely undulating subregion (zone 1), Piedmont alluvial plains (zone 2), central alluvial plains (zone 3), and southwestern alluvial plains (zone 4), varying in rainfall and temperature. Static and temporal variabilities in soil physical and chemical properties prevail because of alluvial parent material, management/tillage operations, and duration of rice–wheat rotation. A detailed survey was undertaken to study the long‐term effect of rice–wheat rotation on soil physical (soil separates, bulk density, modulus of rupture, saturated and unsaturated hydraulic conductivities, soil water content, and suction relations) and chemical (organic carbon, pH, electrical conductivity) properties of different textured soils (sandy clay loam, loam, clay loam, and silty clay loam) in these four zones of Punjab. Soil samples (of 0‐ to 30‐cm depth) from 45 sites were collected during 2006 and were analyzed for physical and chemical properties. The results showed that sand content and pH increased whereas silt and organic carbon decreased significantly from zones 1 to 4. Compared to other textures, significantly greater organic carbon, modulus of rupture, and pH in silty clay loam; greater bulk density in clay loam, and greater saturated hydraulic conductivity in sandy clay loam were observed. Irrespective of zone and soil texture, in the subsurface soil, there was a hard pan at 15–22.5 cm deep, which had high soil bulk density, modulus of rupture, more silt and clay contents (by 3–5%) and less organic carbon and hydraulic conductivity than the surface (0–15 cm) layer. These properties deteriorated with fineness of the soil texture and less organic carbon content. Continuous rice–wheat cropping had a deleterious effect on many soil properties. Many of these soils would benefit from the addition of organic matter, and crop yields may also be affected by the distinct hardpan that exists between 15 and 22.5 cm deep.     

A Pedological Characterisation of Some Inland Wetlands and Ramsar Sites in Algeria

This paper aims to characterise soils of 12 wetlands, of which ten are Ramsar sites, in the ecocomplex of wetlands of the Hauts Plateaux region in Northeast Algeria. Soil samples from every site were collected following the four cardinal directions, along a transect covering the peripheral vegetation belts, and from two depths of the surface horizon. Each soil sample was analysed to determine electrical conductivity, pH, total carbonates, gypsum, chlorides, bicarbonates, sulfates and the particle size. The soil texture and chemical facies (Cl–SO₄–HCO₃) of each site were identified and discussed. Changes in physicochemical parameters were tested according to the spatial features of sites (orientations, vegetation transects and sample depth). A great heterogeneity was found between soils of sampled sites. Indeed, soil physicochemical characteristics differed from one site to another and between belts of the natural vegetation within the same site. Overall, the study wetlands were characterised by salty to very salty soils (electrical conductivity = 3·46 ± 2·44 dS m⁻¹), of neutral to alkaline pH (6·9–8·1), moderately calcareous (CaCO₃ ranged between 15·7% and 33·7%) and little to extremely gypsiferous (gypsium varied from 2·1% to 39·4%). The dominant soil texture classes were medium textures (loam, sandy loam or silty clay loam). Chemically, chlorides (18·5 ± 16·3 Meq/100 g) and/or sulfates (16·5 ± 12·5 Meq/100 g) dominated soil solutions of these environments but with slight bicarbonate contents (0·6 ± 2·6 Meq/100 g). Moreover, there were poor correlations between physicochemical parameters, which indicates interactions between certain parameters under the effect of specific habitat conditions. Copyright © 2015 John Wiley & Sons, Ltd.     

Evaluation of the physicochemical properties of alluvial and colluvial soils formed under ustic moisture regime using multivariate geostatistical techniques

The purpose of this study, which was carried out in the areas of Amasya Gökhöyük Agricultural Enterprise, Turkey, was to determine area management factors that will induce management practices unique to alluvial and colluvial areas using multivariate geostatistical techniques. Physical and chemical analyses were done for 224 soil samples taken at 0–30 cm depth from Entisol and Inceptisol soils. Based on the factor analysis results of the data set prepared, factors were determined, and these factors were named to as soil texture, soil organic matter, fertilization, and pH. While the texture factor accounted for the highest variability with 32.17% and the pH factor accounted for the lowest variability with 10.45%, the four factors together accounted for 79.17% of the total variance. According to the spatial distribution maps, soil texture and soil organic matter factors reached the highest values in alluvial areas close to Çekerek Creek while fertilization factor reached the highest values in colluvial areas. However, pH showed a relatively more homogenous distribution and reached its highest values in areas close to the transition zone of alluvial and colluvial areas. Based on these results, it can be seen that the aforementioned factors are the most important soil factors for these areas.     

SOIL TEXTURE PATTERNS IN THE ALLUVIUM OF THE LOWER INDUS PLAINS

Soil texture was mapped in the immature alluvial soils of the Lower Indus plain. A disadvantage of soil texture as a mapping criterion in such soils is the great complexity of their textural patterns. The geomorphological background of the Lower Indus plains is examined, and a classification of texture and textural profiles is defined. The mapping unit proposed, the‘textural association', comprises a certain range of textural profiles within a given landform, related to each other by the modes of deposition which established that landform. It seems likely that the textural association could, in more detailed surveys, form the basis of a soil series classification.     

应用Markov链理论定量描述区域冲积土壤质地层次的垂向变化特征

冲积土壤剖面质地层次的垂向变化是一个十分复杂的问题,长期以来都是定性描述而无法定量化,但土壤剖面的质地层次组合特点对土壤水分转化和溶质运移等具有重要影响,对其定量地描述和研究是进一步准确定量区域农田水转化和溶质运移的基础。马尔可夫链理论是用来描述随时间（空间）变化的一个离散状态序列的状态转移特性的,本文就其引入来研究冲积土壤剖面质地层次的垂向变化规律。研究结果表明,区域冲积土壤剖面质地层次的垂向变     

区域农田土壤质地剖面的随机模拟模型

冲积土壤剖面的质地层次分层是该类土壤的重要特性,对农田水分转化和溶质运移具有重要影响。本文论据已取得的研究结果,采用Ｍａｒｋｏｖ链理论提出了区域冲积土壤质地层次的随机模拟模型－ＭＣ模型和ＭＣ－ＬＮ模型,采用蒙特卡罗方法模拟了研究区的土壤质地剖面,并与实测结果进行了对比。     

深圳城市绿地土壤肥力质量评价及管理对策

城市绿地是城市生态系统的重要组成部分,被称为城市的"肺"。城市绿地土壤通过其支持的植物、微生物和自身的功能,美化和净化城市环境,对城市的可持续发展具有重要意义。采集深圳市中心城区主要公园绿地、道路绿化带、住宅区绿地和单位附属绿地0～20cm,20～40cm土壤,研究了土壤质地、容重、孔隙度、阳离子交换量、pH、有机质、氮、磷、钾等物理化学性质。结果表明,深圳城市绿地土壤以砂壤和轻壤土为主,20～40cm土壤中松砂和紧砂土占有一定比例,土壤砾石含量高,重砾质土壤占91%以上;表层土壤(0～20cm)容重大,孔隙度小,阳离子交换量低;土壤pH较自然土壤明显增高,以中性和微酸性为主。土壤有机质处于较低的水平;全氮、碱解氮和全磷处于很低水平,有效磷处于中等水平;土壤全钾、速效钾处于中等或以上水平。0～20cm土壤中有机质、全氮、碱解氮显著高于20～40cm土壤。根据深圳城市绿地土壤质量状况,提出了加强深圳城市绿地土壤科学管理的措施和建议。     

基于Hydrus-1D模型的玉米根系吸水影响因素分析

为探索土壤质地、植物生长状况和气象条件对不同土壤水分条件下根系吸水速率的影响机理,该文以相对根吸水速率与土壤含水率的关系衡量土壤水分有效性,利用Hydrus-1D模型模拟了3种土壤（壤黏土、黏壤土和砂壤土）中不同玉米生长状况（包括叶面积指数、根系深度和根系剖面分布）或蒸发力条件下根系吸水速率随含水率的动态变化,确定了不同条件下根系吸水速率开始降低的临界含水率。结果表明：土壤质地、植物的叶面积指数和根系分布及大气蒸发力都对根系吸水动态曲线的临界含水率有一定影响,其中根系深度和根系分布形状还影响根系吸水速率与含水率关系曲线的形状,但在3种土壤中,根系吸水速率的动态变化对植物生长和大气蒸发力的响应不同。总体而言,3种土壤临界含水率的大小是壤黏土＞黏壤土＞砂壤土;临界含水率随大气蒸发力的升高而升高,随根系深度和深层根系分布的增加而降低;各因子对玉米根系吸水影响程度的大小是土壤质地＞根系分布形状＞根系深度＞大气蒸发力＞叶面积指数。     

Spatial variability of Southeastern U.S. Coastal Plain soil physical properties: Implications for site-specific management

Our objectives were to describe the field-scale horizontal and vertical spatial variability of soil physical properties and their relations to soil map units in typical southeastern USA coastal plain soils, and to identify the soil properties, or clusters of properties, that defined most of the variability within the field. The study was conducted on a 12-ha field in Kinston, NC. A 1:2400 scale soil survey had delineated three soil map units in the field: Norfolk loamy sand, Goldsboro loamy sand, and Lynchburg sandy loam. These are representative of millions of hectares of farmland in the Coastal Plain of the southeastern USA. Sixty soil cores were taken to ∼ 1-m depth, sectioned into five depth increments, and analyzed for: soil texture as percentage sand, silt, and clay; soil water content (SWC) at − 33 and − 1500 kPa; plant available water (PAW); saturated hydraulic conductivity (Ksat); bulk density (BD); and total porosity. A penetrometer was used to measure cone index (CI) at each sample location. Variography, two mixed-model analyses, and principal components analysis were conducted. Results indicated that soil physical properties could be divided into two categories. The first category described the majority of the within-field variability and included particle size distribution (soil texture), SWC, PAW, and CI. These characteristics showed horizontal spatial structure that was captured by soil map units and especially by the division between sandy loams and finer loam soils. The second class of variables included BD, total porosity, and Ksat. These properties were not spatially correlated in the field and were unrelated to soil map unit. These findings support the hypothesis that coastal plain soil map units that delineate boundaries between sandy loams versus finer loam soils may be useful for developing management zones for site-specific crop management.     

土壤质地对玉米不同生理指标水分有效性的影响

为确定土壤质地对玉米不同生理指标水分有效性的影响,该文利用3种土壤（重壤土、中壤土和砂壤土）的盆栽控水试验和1种土壤（重壤土）的田间小区控水试验,研究了玉米不同生理指标随相对土壤含水率（土壤含水率占田间持水率的比）的动态变化。结果表明：3种土壤中各生理指标相对值在相对土壤含水率降低到土壤水分阈值之前保持不变,低于此阈值时随相对含水率的进一步降低而线性降低,且均可用分段函数来拟合（R2=0.824～0.999）。土壤水分有效性大小排序为：砂壤土＞中壤土＞重壤土,而且瞬时生理指标的土壤水分阈值低于日变化和整个试验阶段的累积指标。因此土壤质地和不同生理指标的时间尺度都会影响玉米生理指标对土壤水分有效性的响应。     

Identifying potential management zones in a layered soil using several sources of ancillary information

Variation in soil texture has a profound effect on soil management, especially in texturally complex soils such as the polder soils of Belgium. The conventional point sampling approach requires high sampling intensity to take into account such spatial variation. In this study we investigated the use of two ancillary variables for the detailed mapping of soil texture and subsequent delineation of potential management zones for site‐specific management. In an 11.5 ha arable field in the polder area, the apparent electrical conductivity (EC_a) was measured with an EM38DD electromagnetic induction instrument. The geometric mean values of the EC_a measured in both vertical and horizontal orientations strongly correlated with the more heterogeneous subsoil clay content (r = 0.83), but the correlation was weaker with the homogenous topsoil clay content (r = 0.40). The gravimetric water content at wilting point (θg_{(?1.5 MPa)}) correlated very well (r = 0.96) with the topsoil clay content. Thus maps of topsoil and subsoil clay contents were obtained from 63 clay analyses supplemented with 117θg_{(?1.5 MPa)} and 4048EC_a measurements, respectively, using standardized ordinary cokriging. Three potential management zones were identified based on the spatial variation of both top and subsoil clay contents. The influence of subsoil textural variation on crop behaviour was illustrated by an aerial image, confirming the reliability of the results from the small number of primary samples.     

Spatial distribution of soil physical properties of alluvial soils: a geostatistical approach

Knowledge of spatial variation of soil is important in site-specific farming and environmental modeling. Soil particles size and water distribution are most important soil physical properties that governing nearly all of the other attributes of soils. The objectives of this study were to determine the degree of spatial variability of sand, silt and clay contents, and water content at field capacity (FC), permanent wilting point (PWP), and available water content (AWC) of alluvial floodplain soils. Data were analyzed both statistically and geostatistically to describe the spatial distribution of soil physical properties. Soil physical properties showed large variability with greatest variation was observed in sand content (68%). Exponential and spherical models were fit well for the soil physical properties. The nugget/sill ratio indicates except clay all other soil physical properties were moderate spatially dependent (37–70%). Cross-validation of the kriged map shows that prediction of the soil physical properties using semivariogram parameters is better than assuming mean of observed value for any unsampled location. The spatial distribution of water retention properties closely followed the distribution pattern of sand and clay contents. These maps will help to planner to develop the variable rate of irrigation (VRI) for the study area.